Function chooseK

src/orchestration/partition.ts:94–112

Decide how many partitions to create, clamped to every relevant bound.

(units: Unit<T>[], totalWeight: number, opts: PartitionOptions)

/** Decide how many partitions to create, clamped to every relevant bound. */
function chooseK<T>(units: Unit<T>[], totalWeight: number, opts: PartitionOptions): number {
  const u = units.length;
  if (u <= 1) return u; // 0 → 0, 1 → 1
  const ceiling = Math.max(1, Math.floor(opts.concurrencyCeiling ?? 16));
  const minUnits = Math.max(1, Math.floor(opts.minUnitsPerPartition ?? 1));

  let k: number;
  if (opts.maxPartitions !== undefined) {
    k = Math.floor(opts.maxPartitions);
  } else if (opts.targetWeightPerPartition && opts.targetWeightPerPartition > 0) {
    k = Math.ceil(totalWeight / opts.targetWeightPerPartition);
  } else {
    k = ceiling; // default: spread as wide as the ceiling allows
  }

  // Never more partitions than units, than the ceiling, or than minUnits permits.
  k = Math.min(k, u, ceiling, Math.max(1, Math.floor(u / minUnits)));
  return Math.max(1, k);
}

/**
 * Partition `items` into balanced, non-overlapping groups.